Tony Accardo because of the power he had and yielded. Also the respect he demanded and lets not forget the fact that he ran the Outfit for 50 or plus years. During Accardo's reign, the Oufit was at its most powerful and wealthiest.
The other is John " No Nose" DiFronzo. Despite the fact that I have met him and have talked to him, he is shown great respect and made his crew wealthy. Also escaping prosecution after being named as one of the killers in the Spilotro killings is something that should be noted.